Under Balearic law, it is a requirement for any tourist accommodation to collect the IDs of all booked guests and file them in a police database. I personally loathe this policy, and the online filing system is both buggy and not particularly user friendly, and an added burden that we simply don't need, but it's the law, and we have to do it.
We ask guests to send us the data prior to arrival, but nobody ever does, so we have to copy their passports or IDs at time of arrival, and enter them into the database afterwards. It adds time to the check in process.
So, it would indeed be helpful if Airbnb would supply this information in advance.